Treatment of relapsed acute myeloid leukemia with MLL/AF6 fusion after allogeneic hematopoietic stem cell transplantation with gemtuzumab ozogamicin with a long interval followed by donor lymphocyte infusion

Therapeutic Targeting of Acute Myeloid Leukemia by Gemtuzumab Ozogamicin

Acute myeloid leukemia (AML) is a complex hematological malignancy characterized by genetic and clinical heterogeneity and high mortality. Despite the recent introduction of novel pharmaceutical agents in hemato-oncology, few advancements have been made in AML for decades. In the last years, the therapeutic options have rapidly changed, with the approval of innovative compounds that provide new opportunities, together with new challenges for clinicians: among them, on 1 September, 2017 the Food and Drug Administration granted approval for Gemtuzumab Ozogamicin (GO) in combination with daunorubicin and cytarabine for the treatment of adult patients affected by newly diagnosed CD33⁺ AML. Benefits of GO-based regimens were also reported in the pre- and post-transplantation settings. Moreover, several biomarkers of GO response have been suggested, including expression of CD33 and multidrug resistance genes, cytogenetic and molecular profiles, minimal residual disease and stemness signatures. Among them, elevated CD33 expression on blast cells and non-adverse cytogenetic or molecular risk represent largely validated predictors of good response.

Gemtuzumab ozogamicin in acute myeloid leukemia: past, present and future

After being in the therapeutic wilderness for several decades, acute myeloid leukemia has been recently thrust into the limelight with a series of drug approvals. Technical refinements in production, genetic manipulation and chemical modification of monoclonal antibodies led to growing interest in antibodies-based treatment strategies. Much of the focus of these efforts in acute myeloid leukemia has been on CD33 as a target. On September 2, 2017, the U.S. Food and Drug Administration approved gemtuzumab ozogamicin for treatment of relapsed or refractory CD33⁺ acute myeloid leukemia. This signals a new chapter in the long and unusual story of gemtuzumab ozogamicin, which was the first antibody-drug conjugate approved for human use by the Food and Drug Administration. In this review we have analyzed the history of this drug which, among several mishaps, is experiencing a second youth and still represents a field to be further explored.

Gemtuzumab ozogamicin monotherapy prior to stem cell infusion induces sustained remission in a relapsed acute myeloid leukemia patient after allogeneic stem cell transplantation: A case report

RATIONALE

Patients with relapsed acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) have poor prognosis. Many patients are not eligible for 2nd HSCT due to organ dysfunction or other complications that prevent them from tolerating conditioning chemotherapy. In those ineligible patients for 2nd HSCT with myeloablative conditioning regimen, reduced intensity conditioning (RIC) are often used. RIC regimens are less toxic but has a less direct anti-tumor efficacy so that RIC regimens are not suitable for the patients with high tumor burden. To overcome this dilemma, Gemtuzumab Ozogamicin (GO) has been used as a part of RIC regimens to add anti-tumor efficacy. We report here a relapsed AML patient who was treated with GO monotherapy followed by stem cell infusion.

PATIENT CONCERNS

A 25-year-old male with AML experienced relapse 9 months after allo-HSCT.

DIAGNOSIS

Since he had mild renal and cardiac dysfunction and his AML did not progress rapidly, we decided not to give him an intensive chemotherapy. However, after azacitidine (AZA) and donor lymphocyte infusion therapy, his leukemic blasts did not decrease.

INTERVENTIONS

Originally, we had planned to proceed with a 2nd allo-HSCT with RIC regimen that consisted of fludarabine, melphalan and fractionated GO (3 mg/m/dose) on day -21, -18, and -15. However, the patient developed appendicitis after the last dose of GO when his neutrophil was 0 cells/μl. Based on his medical acuity, we terminated the rest of the patients conditioning regimen and the patient did not receive any further chemotherapeutics. The patient was still infused with peripheral blood stem cells from the donor on day 0.

OUTCOMES

His appendicitis was resolved by antibiotics without surgery. His AML has been in CR more than 18 months under AZA maintenance therapy.

LESSONS

GO monotherapy could be a conditioning regimen of 2nd allo HSCT from the same donor as the first HSCT for relapsed AML patients.

Biomarkers of Gemtuzumab Ozogamicin Response for Acute Myeloid Leukemia Treatment

Gemtuzumab ozogamicin (GO, Mylotarg®) consists of a humanized CD33-targeted antibody-drug conjugated to a calicheamicin derivative. Growing evidence of GO efficacy in acute myeloid leukemia (AML), demonstrated by improved outcomes in CD33-positive AML patients across phase I to III clinical trials, led to the Food and Drug Administration (FDA) approval on 1 September 2017 in CD33-positive AML patients aged 2 years and older. Discrepancies in GO recipients outcome have raised significant efforts to characterize biomarkers predictive of GO response and have refined the subset of patients that may strongly benefit from GO. Among them, CD33 expression levels, favorable cytogenetics (t(8;21), inv(16)/t(16;16), t(15;17)) and molecular alterations, such as NPM1, FLT3-internal tandem duplications and other signaling mutations, represent well-known candidates. Additionally, in depth analyses including minimal residual disease monitoring, stemness expression (LSC17 score), mutations or single nucleotide polymorphisms in GO pathway genes (CD33, ABCB1) and molecular-derived scores, such as the recently set up CD33_PGx6_Score, represent promising markers to enhance GO response prediction and improve patient management.

Management of relapse after allo-SCT for AML and the role of second transplantation

Relapse after allo-SCT for AML carries very poor prognosis. Second allo-SCT, although curative, is not an appropriate treatment option for a large number of relapsing patients (only 2-20% patients receive a second allo-SCT), and efforts to increase the number of patients who may benefit from a second allo-SCT are ongoing. In addition, understanding the varied biological processes that are operative in disease relapse has encouraged the development of novel therapies, and could be beneficial to patients who are currently managed conservatively with supportive care for relapsed disease. Incorporating novel combinations of drugs with immunomodulation, although theoretically attractive, should be tested in the setting of clinical trials. In this review, we discuss the currently available approaches for relapsed AML after allo-SCT.